U.S. Pat. No. 6,605,674 describes the preparation of structurally-modified cationic polymers where monomers are polymerized under free radical polymerization conditions in which a structural modifier is added to the polymerization after about 30 percent polymerization of the monomers has occurred and use of the polymers as retention and drainage aids in papermaking processes.
The use of medium molecular weight diallyldimethylammonium chloride/acrylamide copolymers as retention and drainage aids is reviewed in Hunter et al., “TAPPI 99 Preparing for the Next Millennium”, vol. 3, pp. 1345-1352, TAPPI Press (1999).
U.S. Pat. No. 6,071,379 discloses the use of diallyl-N,N-disubstituted ammonium halide/acrylamide dispersion polymers as retention and drainage aids in papermaking processes.
U.S. Pat. No. 5,254,221 discloses a method of increasing retention and drainage in a papermaking process using a low to medium molecular weight diallyldimethylammonium chloride/acrylamide copolymer in combination with a high molecular weight dialkylaminoalkyl (meth)acrylate quaternary ammonium salt/acrylamide copolymer.
U.S. Pat. No. 6,592,718 discloses a method of improving retention and drainage in a papermaking furnish comprising adding to the furnish a diallyl-N,N-disubstituted ammonium halide/acrylamide copolymer and a high molecular weight structurally-modified, water-soluble cationic polymer.
U.S. Pat. Nos. 5,167,776 and 5,274,055 disclose ionic, cross-linked polymeric microbeads having a diameter of less than about 1,000 nm and use of the microbeads in combination with a high molecular weight polymer or polysaccharide in a method of improving retention and drainage of a papermaking furnish.
Nonetheless, there is a continuing need for new compositions and processes to further improve retention and drainage performance, particularly for use on the faster and bigger modern papermaking machines currently being put into use.